PROGRAM f07npfe

!      F07NPF Example Program Text

!      Mark 23 Release. NAG Copyright 2011.

!      .. Use Statements ..
       USE nag_library, ONLY : nag_wp, x04dbf, zsysvx
!      .. Implicit None Statement ..
       IMPLICIT NONE
!      .. Parameters ..
       INTEGER, PARAMETER              :: nb = 64, nin = 5, nout = 6
!      .. Local Scalars ..
       REAL (KIND=nag_wp)              :: rcond
       INTEGER                         :: i, ifail, info, lda, ldaf, ldb, ldx, &
                                          lwork, n, nrhs
!      .. Local Arrays ..
       COMPLEX (KIND=nag_wp), ALLOCATABLE :: a(:,:), af(:,:), b(:,:), work(:), &
                                             x(:,:)
       REAL (KIND=nag_wp), ALLOCATABLE :: berr(:), ferr(:), rwork(:)
       INTEGER, ALLOCATABLE            :: ipiv(:)
       CHARACTER (1)                   :: clabs(1), rlabs(1)
!      .. Executable Statements ..
       WRITE (nout,*) 'F07NPF Example Program Results'
       WRITE (nout,*)
       FLUSH (nout)
!      Skip heading in data file
       READ (nin,*)
       READ (nin,*) n, nrhs
       lda = n
       ldaf = n
       ldb = n
       ldx = n
       lwork = nb*n
       ALLOCATE (a(lda,n),af(ldaf,n),b(ldb,nrhs),work(lwork),x(ldx,nrhs), &
          berr(nrhs),ferr(nrhs),rwork(n),ipiv(n))

!      Read the upper triangular part of A from data file

       READ (nin,*) (a(i,i:n),i=1,n)

!      Read B from data file

       READ (nin,*) (b(i,1:nrhs),i=1,n)

!      Solve the equations AX = B for X
!      The NAG name equivalent of zsysvx is f07npf
       CALL zsysvx('Not factored','Upper',n,nrhs,a,lda,af,ldaf,ipiv,b,ldb,x, &
          ldx,rcond,ferr,berr,work,lwork,rwork,info)

       IF ((info==0) .OR. (info==n+1)) THEN

!         Print solution, error bounds and condition number

!         ifail: behaviour on error exit
!                =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
          ifail = 0
          CALL x04dbf('General',' ',n,nrhs,x,ldx,'Bracketed','F7.4', &
             'Solution(s)','Integer',rlabs,'Integer',clabs,80,0,ifail)

          WRITE (nout,*)
          WRITE (nout,*) 'Backward errors (machine-dependent)'
          WRITE (nout,99999) berr(1:nrhs)
          WRITE (nout,*)
          WRITE (nout,*) 'Estimated forward error bounds (machine-dependent)'
          WRITE (nout,99999) ferr(1:nrhs)
          WRITE (nout,*)
          WRITE (nout,*) 'Estimate of reciprocal condition number'
          WRITE (nout,99999) rcond
          WRITE (nout,*)

          IF (info==n+1) THEN
             WRITE (nout,*)
             WRITE (nout,*) 'The matrix A is singular to working precision'
          END IF
       ELSE
          WRITE (nout,99998) 'The diagonal block ', info, ' of D is zero'
       END IF

99999  FORMAT ((3X,1P,7E11.1))
99998  FORMAT (1X,A,I3,A)
    END PROGRAM f07npfe